A group of time - traveling historians. They accidentally cross paths with Addie during one of their trips. They are fascinated by her and want to study her unique situation. This could bring in elements of different time periods as they try to figure out how Addie has survived for so long. Their presence could also put Addie in danger as they might accidentally expose her to the wrong people.
Addie Larue herself is of course the most important character. She is the one with the strange curse of immortality and invisibility in a sense. Henry is also very important. He is the one who can remember Addie, and their relationship is central to the story. Then there are the various people Addie meets throughout the centuries, like the villagers in her hometown at the start, who play a role in shaping her understanding of the world and her situation.
One idea could be exploring Addie's encounters with different historical figures in more depth. For example, how she influenced or was influenced by them during specific events. Another could be a story where she tries to find a way to reverse her curse in a new and unexpected way, perhaps with the help of a modern-day character who has some unique knowledge or ability.
One of the main themes is the passage of time. Addie experiences centuries, which shows how time can change things yet some aspects of human nature remain the same. Another theme is identity. As she lives invisibly for so long, she has to constantly re - evaluate who she is. Also, love is a theme. Her relationship with Henry makes her question what love means when she has such a different existence from normal humans.
A group of nomadic mice. They have different skills and traditions compared to the Redwall mice. Their arrival at the abbey could cause some cultural clashes at first, but eventually, they could learn from each other and contribute to the abbey's growth. This would add more diversity to the characters in the fanfiction.
A young stargazer from Earth could be a new character. This character could be someone who has always been fascinated by the stars and dreams of traveling to other planets. When the Little Prince lands on Earth again, they meet and the stargazer becomes his guide on Earth, showing him all the new things that have happened since his last visit. Another potential character could be a talking moonbeam. It could offer the Little Prince advice and wisdom, as well as some magical abilities to help him on his journey.
A new character could be a therapist who has a unique approach to helping the main character. This therapist could introduce new ideas and methods of healing that the main character hasn't encountered before.
A healer from a far - off land could be an interesting addition. This character could bring in new knowledge of magic and medicine that the existing characters are unaware of. Maybe they have a special connection to nature that allows them to heal in ways not seen before in the story.
A young Martian inventor could be a great addition. This character could create unique gadgets and machines that help the protagonists in their adventures. For example, a flying device that can travel at high speeds across Mars.
A mysterious traveler passing through the town could be a new character. This person has seen many strange things in their travels and is not afraid of Edward. In fact, they see his potential and encourage him to leave the town and see the world.
A healer character could be added. This healer could be the one who discovers a hidden power within the apprentice that could change the course of their journey. Another potential character could be a mysterious traveler. This traveler has seen many different worlds and has knowledge that could either help or hinder the apprentice.